Concentration measuring instrument, and method of measuring the concentration of a specific component in a subject of measurement

ABSTRACT

To provide a measuring method which enables a highly accurate measurement of concentrations of specific components in subjects of measurement even when the concentration measuring contact of a concentration measuring instrument is contaminated with drinks or the like. 
     The concentration measuring instrument includes: 
     a main body that has a concentration measuring contact, a light source and a photodetector; and 
     judging means that calculates the difference between a non-contact-measured value, a value, measured by the photodetector while keeping a subject of measurement out of contact with the concentration measuring contact, of the quantity of light that is emitted and entered by the light source into the concentration measuring contact and returned to the concentration measuring contact and a predetermined reference value obtained in advance by making measurement while keeping the concentration measuring contact clean and judges whether the calculation of the concentration of the specific component in the subject of measurement is effective or not by comparing the calculated difference with a predetermined threshold.

This Application is a U.S. National Phase Application of PCTInternational Application PCT/JP03/03187.

TECHNICAL FIELD

The present invention relates to a concentration measuring instrument ofmeasuring concentrations of glucose, cholesterol, ethanol, thederivatives of cholesterol, etc. which are contained in subjects ofmeasurement, such as living body tissues.

BACKGROUND ART

A variety of methods have been proposed which measure specificcomponents in specimens, particularly in living bodies and solutionsusing an attenuated total reflectance (hereinafter referred to as ATR)measuring instrument.

For example, in Japanese Patent Laid-Open No. 9-113439, there isproposed a method of measuring the blood sugar level using a transparentATR device 51 having a pair of parallel reflecting surfaces opposingeach other in which measurement is made with upper and lower lips 52, asa specimen, brought into tight contact with the ATR device 51, as shownin FIG. 7. The entire disclosure of Japanese Patent Laid-Open No.9-113439 is incorporated herein by reference in its entirety. Accordingto this method, the measurement of the blood sugar level is made throughthe following procedures: inserting an ATR device 51 between upper andlower lips, and getting the same to be hold firmly by the lips; enteringlight into the ATR device 51 so that the light is allowed to undergototal reflection repeatedly at the interface between each reflectionsurface of the ATR device 51 and the lips 52, as shown by the brokenline in FIG. 7; and analyzing the light that oozes out of the ATR device51.

In BME, Vol. 5, No. 8 (Japan ME Society, 1991), there is proposed amethod which measures the blood sugar level, the concentration ofethanol in blood, etc. using an ATR device made up of ZnSe opticalcrystal etc. In the method, measurements are made through the followingprocedures: bringing the ATR device into tight contact with lip mucosa;entering a laser light with a wavelength of 9 to 11 microns into the ATRdevice and allowing the light to undergo multiple reflection inside theATR device; and analyze the absorbed and scattered light. The entiredisclosure of BME, Vol. 5, No. 8 (Japan ME Society, 1991) isincorporated herein by reference in its entirety. According to thismethod, concentrations of specific components such as glucose, ethanoland cholesterol can be measured non-invasively and in real time. Thismethod is to apply evanescent light (known as ooze-out light) to aquantitative analysis. Only a very small quantity of the light travelingin the ATR device actually enters lips, and the light having entered thelips is affected by components in the body fluid existing in the lips.For example, in glucose, its light absorption peaks at a wave number of1080 cm⁻¹; therefore, when applying light with the above wave number toa living body, the quantity of the light absorption of glucose changesdepending on the glucose concentration in the living body. Accordingly,if the quantity of the light returned from the living body is measured,the change in quantity of the light absorption of a component in bodyfluid with change in the concentration of the component can be detected,in other words, the concentration of the component can be obtained.

When measuring the absorbance of a substance surface with an ATRmeasuring instrument and calculating the concentration of the same usingthe measured absorbance, the measuring method shown in FIG. 8 has beencommonly used.

First, in the background measuring step, the measurement of backgroundis made by entering light emitted by a light source into the ATR device,carrying out spectrometry of a reference, such as air or deionizedwater, while keeping the ATR device out of contact with a sample as asubject of measurement, and storing the measured results in a memory(S8). The reasons for the background measurement are to correct thewavelength characteristics of a light source and a photodetector and toensure an accurate absorbance measurement or concentration calculationeven after their characteristics have changed with time.

Then, the sample as a subject of measurement is set so that it comes incontact with the ATR device (S9) and measurement is made for the sample(S10).

Calculation is carried out according to the following equation, Log₁₀(Ib/Im), where Ib represents a detected signal from the photodetector atthe time of background measurement and Im a detected signal from thephotodetector at the time of measurement for the sample. The calculatedvalue is commonly referred to as absorbance. Since absorbance correlateswith concentration of a specific components in a sample, if acalibration curve of absorbance and concentration is prepared inadvance, the concentration of a specific component in the sample can beestimated from the calculated absorbance (S11).

The conventional ATR measuring instruments described above, however,have the following problems.

When the surface of the ATR device is contaminated or the residues leftat the last measurement adhere on the surface of the device at the timeof background measurement, the accuracy of the measurement for specificcomponents decreases.

For example, when measuring the glucose concentration in lip mucosa, ifthe mouse is not sufficiently rinsed, components of teas, juices or thelike remain on the lip mucosa, which has an adverse effect on themeasured results.

DISCLOSURE OF THE INVENTION

The present invention has been made in the light of the above describedproblems. Accordingly, the object of the invention is to provide aconcentration measuring instrument, and a method of measuring theconcentration of a specific component in a subject of measurement whichenables a highly accurate measurement of the concentration of a specificcomponent in a subject of measurement even when its concentrationmeasuring contact is contaminated by drinks etc. adhering on itssurface.

To solve the above problems, a first aspect of the present invention isa concentration measuring instrument, comprising:

a main body that has a concentration measuring contact, a light sourcethat emits light and enters the light into the concentration measuringcontact, and a photodetector; and

judging means that

calculates the difference between a non-contact measured value, a value,measured by the photodetector while keeping a subject of measurement outof contact with the concentration measuring contact, of the quantity oflight which is emitted and entered by the light source into theconcentration measuring contact, passed through or oozed from theconcentration measuring contact to the outside thereof and returned tothe concentration measuring contact and a predetermined reference value,a value, measured by the photodetector while keeping the concentrationmeasuring contact clean, of the quantity of the light which is emittedand entered by the light source into the concentration measuringcontact, passed through or oozed from the concentration measuringcontact to the outside thereof and returned to the concentrationmeasuring contact, and

judges whether the calculation of the concentration of a specificcomponent in the subject of measurement is effective or not by comparingthe calculated difference with a predetermined threshold.

A second aspect of the present invention is the concentration measuringinstrument according to the first aspect of the present invention,further comprising calculating means, wherein

the photodetector (6) measures, while keeping the subject of measurementin contact with the concentration measuring contact (2), the quantity oflight which is emitted and entered by the light source (1) into theconcentration measuring contact (2), passed through the concentrationmeasuring contact (2) into a subject of measurement, transmitted in thesubject of measurement, and returned to the concentration measurementcontact, when the judging means (8) judges the calculation of theconcentration of a specific component in the subject of measurement tobe effective, and

the calculating means (10) calculates the concentration of a specificcomponent in the subject of measurement based on a contact measuredvalue, a value obtained by making measured while keeping the subject ofmeasurement in contact with the concentration measuring contact (2).

A third aspect of the present invention is the concentration measuringinstrument according to the first aspect of the present invention,further comprising indicating means, wherein the indicating means givesa message that indicates the surface of the concentration measuringcontact should be cleaned, when the judging means judges the calculationof the concentration of a specific component in the subject ofmeasurement to be ineffective.

A fourth aspect of the present invention is a concentration measuringinstrument, including:

a main body that has a concentration measuring contact, a light sourcethat emits light and enters the light into the concentration measuringcontact, and a photodetector; and

judging means that

calculates the difference between (1) a non-contact measured value, avalue, measured by the photodetector, of the quantity of light which isemitted and entered by the light source into the concentration measuringcontact once brought into contact with the subject of measurement andthen kept out of contact with the same, passed through or oozed from theconcentration measuring contact to the outside thereof and returned tothe concentration measuring contact and (2) a predetermined referencevalue, a value, measured by the photodetector while keeping theconcentration measuring contact clean, of the quantity of light which isemitted and entered by the light source into the concentration measuringcontact, passed through or oozed from the concentration measuringcontact to the outside thereof and returned to the concentrationmeasuring contact, and

A fifth aspect of the oresent invention is the concentration measuringinstrument of the fourth aspect of the present invention, furtherincluding calculating means, wherein

the photodetector measures, while keeping the subject of measurement incontact with the concentration measuring contact, the quantity of lightwhich is emitted and entered by the light source into the concentrationmeasuring contact, passed through the concentration measuring contactinto the subject of measurement, transmitted in the subject ofmeasurement, and returned to the concentration measurement contact and

compares the calculated difference with a predetermined threshold so asto judge whether the calculation of the concentration of a specificcomponent in the subject of measurement is effective or not.

A fifth invention is the concentration measuring instrument of thefourth invention, further including calculating means (10), wherein

the photodetector (6) measures, while keeping the subject of measurement(2) in contact with the concentration measuring contact (2), thequantity of light which is emitted and entered by the light source (1)into the concentration measuring contact (2), passed through theconcentration measuring contact (2) into the subject of measurement,transmitted in the subject of measurement, and returned to theconcentration measurement contact (2) and

when the judging means judges the calculation of the concentration of aspecific component in the subject of measurement to be effective, thecalculating means calculates the concentration of the specific componentin the subject of measurement based on a contact measured value, whichis a value measured while keeping the subject of measurement in contactwith the concentration measuring contact.

A sixth aspect of the present invention is the concentration measuringinstrument of the fourth aspect of the present invention, furtherincluding indicating means, wherein the indicating means gives a messagethat indicates the subject of measurement should be cleaned, when thejudging means judges the calculation of the concentration of a specificcomponent in the subject of measurement to be ineffective.

A seventh aspect of the present invention is a concentration measuringinstrument, including:

a main body that has a concentration measuring contact, a light sourcethat emits light and enters the light into the concentration measuringcontact and a photodetector;

input means that inputs (1) a contact-measured value, a value, measuredby the photodetector, of the quantity of light which is emitted andentered by the light source into the concentration measuring contact incontact with a subject of measurement, passed through the concentrationmeasuring contact into the subject of measurement, transmitted in thesubject of measurement, and returned to the concentration measuringcontact and (2) a non-contact measured value, a value, measured aftermeasuring the contact-measured value by the photodetector and keepingthe subject of measurement out of contact with the concentrationmeasuring contact, of the quantity of light which is emitted and enteredby the light source into the concentration measuring contact, passedthrough or oozed from the concentration measuring contact to the outsidethereof and returned to the concentration measuring contact;

correcting means that corrects the contact-measured value using thenon-contact-measured value; and

calculating means that calculates the concentration of a specificcomponent contained in the subject of measurement based on the correctedresult.

An eighth aspect of the present invention is the concentration measuringinstrument according to anyone of the first to the seventh aspects ofthe present invention, wherein the concentration measuring contact is anattenuated total reflectance device and the light entered into theconcentration measuring contact is evanescent light oozed from theattenuated total reflectance device.

A ninth aspect of the present invention is the concentration measuringinstrument according to any one of the first to the seventh asoects ofthe present invention, wherein the subject of measurement is a livingbody tissue and the specific component is glucose, ethanol, cholesterol,or the derivative of cholesterol.

A tenth aspect of the present invention is the concentration measuringinstrument according to any one of the first to the seventh aspects ofthe present invention, wherein the photodetector scans the light in thewave number region of 1000 cm⁻¹ to 1200 cm⁻ centered at 1100 cm⁻¹.

An eleventh aspect of the present invention is the concentrationmeasuring instrument of the seventh aspect of the present invention,wherein the correcting means calculates a value by subtracting theabsorbance to the light with a specific wave number, which is calculatedfrom the non-contact measured value, from the absorbance to the lightwith a specific wave number, which is calculated from thecontact-measured value, and

the calculating means calculates the concentration of the specificcomponent contained in the subject of measurement based on the valuecalculated by the correcting means.

A twelfth aspect of the present invention is the concentration measuringinstrument according to any one of the first to the sixth aspects of thepresent invention, wherein the judging means judges the calculation ofthe concentration of a specific component in the subject of measurementto be ineffective, when the absorbance to the light with a specific wavenumber which is obtained from the non-contact-measured value is largerthan a predetermined value.

A thirteenth aspect of the present invention is the concentrationmeasuring instrument according to any one of the first to the sixthaspects of the present invention, wherein

the measurement of the non-contact-measured value is to measure, by thephotodetector, the quantities of the p-polarized light component and thes-polarized light component of the light which is emitted and entered bythe light source into the concentration measuring contact out of contactwith the subject of measurement, passed through or oozed from theconcentration measuring contact to the outside thereof, and returned tothe concentration measuring contact,

the judging means judges whether or not there exists a contaminantadhering on the surface of the concentration measuring contact, based onthe measured values of the quantities of the p-polarized light componentand the s-polarized light component, and

the judgment of whether the calculation of the concentration of aspecific component in the subject of measurement is effective or not isto judge whether or not there exists a contaminant adhering on thesurface of the concentration measuring contact.

A fourteenth aspect of the present invention is the concentrationmeasuring instrument according to the thirteenth aspect of the presentinvention, wherein the judging means carries out calculation accordingto the equation, Ip/Is or log₁₀ (Ip/Is), where Ip represents themeasured value of the quantity of the p-polarized light component and Isthe measured value of the quantity of the s-polarized light component,and judges that there exists a contaminant adhering on the surface ofthe concentration measuring contact, when the calculated value is thesame as or more than a given value.

A fifteenth aspect of the present invention is the concentrationmeasuring instrument according to the fourteenth aspect of the presentinvention, wherein the judging means judges that there exists nocontaminant adhering on the surface of the concentration measuringcontact when the value of Ip/Is is in the range of 0.9 to 1.1.

A sixteenth aspect of the present invention is the concentrationmeasuring instrument according to the thirteenth aspect of the presentinvention, wherein the judging means carries out calculation accordingto the equation, Is/Ip or log₁₀ (Is/Ip), where Ip represents themeasured value of the quantity of the p-polarized light component and Isthe measured value of the quantity of the s-polarized light component,and judges that there exists a contaminant adhering on the surface ofthe concentration measuring contact, when the calculated value is thesame as or less than a given value.

A seventeenth aspect of the present invention is the concentrationmeasuring instrument according to the sixteenth aspect of the presentinvention, wherein the judging means judges that there exists nocontaminant adhering on the surface of the concentration measuringcontact when the value of Is/Ip is in the range of 0.9 to 1.1.

An eighteenth aspect of the present invention is a method of measuringthe Image Page 9 concentration of a specific component in a subject ofmeasurement utilizing the main body of a concentration measuringinstrument that has a concentration measuring contact, a light sourcethat emits light and enters the light into the concentration measuringcontact and a photodetector, including:

a non-contact measuring step of measuring, by the photodetector whilekeeping the subject of measurement out of contact with the concentrationmeasuring contact, the quantity of light which is emitted and entered bythe light source into the concentration measuring contact, passedthrough or oozed from the concentration measuring contact to the outsidethereof and returned to the concentration measuring contact; and

a judging step of judging whether the calculation of the concentrationof the specific component in the subject of measurement is effective ornot by comparing with a predetermined threshold a calculated differenceobtained by subtracting a predetermined reference value, a value,measured by the photodetector while keeping the concentration measuringcontact clean, of the quantity of light which is emitted and entered bythe light source into the concentration measuring contact, passedthrough or oozed from the concentration measuring contact to the outsidethereof and returned to the concentration measuring contact from anon-contact measured value, a value measured in the non-contactmeasuring step.

A nineteenth aspect of the present invention is a method of measuringthe concentration of a specific component in a subject of measurementutilizing the main body of a concentration measuring instrument that hasa concentration measuring contact, a light source that emits light andenters the light into the concentration measuring contact and aphotodetector, including:

a non-contact measuring step of measuring by the photodetector thequantity of light which is emitted and entered by the light source intothe concentration measuring contact which is once brought into contactwith the subject of measurement and then kept out of contact with thesame, passed through or oozed from the concentration measuring contactto the outside thereof and returned to the concentration measuringcontact; and

a judging step of judging whether the calculation of the concentrationof a specific component in the subject of measurement is effective ornot by comparing with a predetermined threshold a calculated differenceobtained by subtracting a predetermined reference value, a value,measured by the photodetector while keeping the concentration measuringcontact clean, of the quantity of light which is emitted and entered bythe light source into the concentration measuring contact, passedthrough or oozed from the concentration measuring contact to the outsidethereof and returned to the concentration measuring contact from anon-contact measured value, which is a value measured in the non-contactmeasuring step.

A twentieth aspect of the present invention is a method of measuring theconcentration of a specific component in a subject of measurement,including:

a contact measuring step of measuring by the photodetector the quantityof light which is emitted and entered by the light source into theconcentration measuring contact in contact with the subject ofmeasurement, passed through the concentration measuring contact into thesubject of measurement, transmitted in the subject of measurement, andreturned to the concentration measuring contact;

a non-contact measuring step of measuring by the photodetector thequantity of light which is emitted and entered by the light source intothe concentration measuring contact, which is kept out of contact withthe subject of measurement after the contact measuring step, passedthrough or oozed from the concentration measuring contact to the outsidethereof, and returned to the concentration measuring contact; and

a calculating step of calculating, after correcting the measured resultobtained in the contact measuring step with the measured result obtainedin the non-contact measuring step, the concentration of the specificcomponent in the subject of measurement based on the corrected result.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic diagram of a concentration measuring instrumentwhich is used in a method of measuring the concentration of a specificcomponent in a specimen in accordance with one embodiment of the presentinvention;

FIG. 2 is a schematic diagram showing the measurement flow of the methodof measuring the concentration of the specific component in thespecimen;

FIG. 3 illustrates characteristic curves showing the spectralcharacteristics in the second spectrometry of the method of measuringthe concentration of the specific component in the specimen;

FIG. 4 illustrates characteristic curves showing the spectralcharacteristics of teas and water;

FIG. 5 is a schematic diagram of another concentration measuringinstrument which is used in a method of measuring the concentration of aspecific component in a specimen in accordance with one embodiment ofthe present invention;

FIG. 6 illustrates characteristic curves showing the spectralcharacteristics obtained in one step of the method of measuring theconcentration of a specific component in a specimen in accordance withanother embodiment of the present invention, in which judgment is madewhether or not there exists a contaminant adhering to the surface of theconcentration measuring contact;

FIG. 7 is a schematic view of a conventional ATR measuring instrument;and

FIG. 8 is a schematic diagram showing the measurement flow of theconventional method of measuring the concentration of a specificcomponent in a specimen.

DESCRIPTION OF SYMBOLS

-   1 Light Source-   2 Concentration Measuring Contact-   3 Light Input Portion-   4 Contact Portion-   5 Light Output Portion-   6 Photodetector-   7 Polarizer-   51 ATR device-   52 Lips

BEST MODE FOR CARRYING OUT THE INVENTION

In the following, embodiments of the present invention will be describedwith reference to the accompanying drawings.

(Embodiment 1)

First, a first embodiment will be described.

FIG. 1 is a schematic diagram of a concentration measuring instrumentwhich is used in a method of measuring the concentration of specificcomponents in subjects of measurement in accordance with one embodimentof the invention.

With this embodiment, one case will be described in which aconcentration of glucose, as a specific component in a subject ofmeasurement, is measured.

As a light source 1, a light source that emits mid-infrared light isused. In this embodiment, a SiC light source is used as the light source1. The SiC light source is particularly suitable for makingconcentration measurements for substances whose absorption wave numberis in the fingerprint region (mid-infrared region) of, for example, 1080cm⁻¹ and 1033 cm⁻¹.

As a material for a concentration measuring contact 2, is preferablyused a material which is capable of transmitting mid-infrared light,chemically stable and excellent in mechanical strength. In thisembodiment, germanium is used as the material for the concentrationmeasuring contact 2.

A contact portion 4 is brought into contact with a subject ofmeasurement. For example, when measuring the concentration of a glucosesolution, the glucose solution is dropped onto the contact portion 4 sothat the solution covers the entire surface of the contact portion 4.The glucose solution never overflows the contact portion 4, due to theeffect of its surface tension, and a suitable amount of solutionrequired for the concentration measurement is kept on the contactportion 4, which allows stable measurement of the glucose concentrationin the solution.

When the subject of measurement is a living body, the living body isbrought into tight contact with the contact portion 4. In this case, thearea of the portion which is in tight contact with the living body ispreferably 2 cm² or less. When the area is about 2 cm² or less, thecontact portion eats deeper into the living body and its contact withthe living body becomes much tighter, which allows stable measurements.As for the portion of the living body which is brought into tightcontact with the contact portion 4, the portion whose stratum corneum isthin is preferable, specifically proximal nail wall at the base of afinger-nail, lips and oral mucosa are preferable.

Preferably the shape of the contact portion 4 is, but not limited to,approximately circular. The reason is that when the subject ofmeasurement is a living body, the circular shape lessens the pain thesubject suffers at the time of measurement. More preferably theperiphery of the contact portion 4 is provided with a chambered portionor a rounded portion, because providing such portions much lessens thepain of the subject.

As a photodetector 6, an MCT photodetector is used in this embodiment.

A polarizer 7 functions to take out a specific component of polarizedlight. In this embodiment, a wire grid polarizer is used in which aplurality of fine slits are provided. Rotating the polarizer 7 makes itpossible to arbitrarily set the component of polarized light thatreaches the photodetector 6 to s-polarized light or p-polarized light.The position of the polarizer 7 is not limited to the position shown inFIG. 1, it has only to be positioned on the optical path between thelight source 1 and the photodetector 6.

In FIG. 1, the direction shown by the solid line on the polarizer 7denotes the vibration direction of the s-polarized light component andthe direction shown by the broken line the vibration direction of thep-polarized light component. The polarizer 7 transmits light in the samevibration direction alone; therefore, measurement of the p-polarizedlight component, after measurement of the s-polarized light component inwhich the component of polarized light is set to the direction shown bythe solid line, can be made just by rotating the polarizer 7 at an angleof 90 degrees.

Providing, for example, spectroscopic means (not shown in the figure)between the light source 1 and the concentration measuring contact 2 ispreferable, because it allows the measurement of the wavelength-spectralcharacteristics of the specific component and obtaining the absorptioncharacteristics of the same at different wavelengths. The spectroscopy,FT-IR method, which uses an interferometer is particularly preferable asspectroscopic means, because it allows highly sensitive measurement.

Judging means 8 judges whether the calculation of the concentration ofthe specific component in a subject of measurement is effective or not.

Calculating means 10 calculates the concentration of a glucose solutionfrom the measurements obtained by the photodetector 6 utilizing acalibration curve 9. As the calculating means 10, a microcomputer or apersonal computer made up of a CPU and a memory is used.

The calibration curve 9 is a collection of data obtained through thefollowing procedures: measuring in advance concentrations of glucosesolutions, whose concentrations are already known, by the method ofmeasuring the concentration of specific components in the specimen inaccordance with the embodiment of the present invention; and getting themeasured results to have one to one correspondence to the knownconcentrations of glucose solutions. The calibration curve 9 is storedin, for example, the above described microcomputer or personal computerin advance.

The indicating means 11 indicates measurement results obtained at thephotodetector 6, messages to the operator and the like.

Then, the method of measuring the concentration of specific componentsin the specimen in accordance with this embodiment, which uses the abovedescribed measuring instrument, will be described taking the case inwhich a glucose concentration is measured through subject's lip mucosa.FIG. 2 is a schematic diagram showing the measurement flow of the methodof measuring the concentration of specific components in the specimen inaccordance with this embodiment.

As shown in FIG. 2, first, background is measured (S1). The measurementof background is made, while keeping subject's lip mucosa out of tightcontact with the contact portion 4 shown in FIG. 1, through thefollowing procedures: entering light emitted by the light source 1 intothe light input portion 3 of the concentration measuring contact 2; andmeasuring the quantity of light, by the photodetector 6, which is passedthrough the contact portion 4 to its outside, returned back to thecontact portion 4, and output from the light output portion 5 to theoutside of the concentration measuring contact 2. In this measurement,the polarizer 7 may be set to p-polarized light or s-polarized light.Spectrometry may be made with the entire surface of the contact portion4 covered and moistened with water. Then, the subject's lip mucosa isbrought into contact with the contact portion 4 (S2) and a firstspectrometry (measurement 1) is made (S3). This measurement is made withthe polarizer 7 set to the same polarized light component as that ofbackground measurement. Like the case of background measurement, themeasurement is made through the following procedures: entering lightemitted by the light source 1 into the light input portion 3 of theconcentration measuring contact 2; and measuring the quantity of light,by the photodetector 6, which is passed through the contact portion 4into the lip mucosa of a subject, returned back to the contact portion 4after transmitted in the lip mucosa, and output from the light outputportion 5 to the outside of the concentration measuring contact 2. Then,the calculating means 10 carries out calculation according to theequation, log₁₀ (Ib/Im1), where Ib represents the value obtained by thebackground measurement and Im1 the value obtained by the firstspectrometry. And the calculated value is taken as absorbance of the lipmucosa.

Then, the contact portion 4 is detached from the lip mucosa (S4) and asecond spectrometry (measurement 2) is made (S5) in the same manner asthe measurement of background without wiping away saliva andcontaminants adhering to the surface of the contact portion 4. Thecalculating means 10 carries out calculation according to the equation,log₁₀ (Ib/Im2), where Im2 represents the value obtained by the secondspectrometry, to give absorbance of the saliva or a contaminant.

One example of spectral characteristics obtained by carrying outcalculation according to the equation, log₁₀ (Ib/Im2), is shown in FIG.3. When measurement is made properly, since the most part of thecomponents of the body fluid remaining on the contact portion is saliva,the spectral characteristics are those at a normal time shown in FIG. 3.The term “characteristics at a normal time” herein used meanscharacteristics obtained by making spectrometry with the surface of thecontact portion 4 moistened with water. However, when makingspectrometry through oral mucosa of a subject with the oral mucosa notgiven a sufficient rinse after the subject drinks tea, juice or thelike, the spectral characteristics are those after having tea shown inthe same figure and sometimes largely different from those at a normaltime. It is known from the figure that, compared with thecharacteristics at a normal time, the absorbance after having tea islarge as a whole, in addition, the spectral line shape is changed in thewave number region of about 1200 cm⁻¹ to about 1000 cm⁻¹ centered atabout 1100 cm⁻¹ where the light absorption of glucose reaches a peak.The value of the absorbance is about 0.02±0.02 at a normal time andabout 0.06±0.02 after having tea.

The absorbance curves of tea and water are shown in FIG. 4. In the samefigure, the one dot-dash line represents the absorbance at a normaltime, the broken line the absorbance of relatively weak tea, and thesolid line the absorbance of relatively strong tea. The term “theabsorbance at a normal time” herein used means the spectralcharacteristics obtained by making spectrometry with the surface of thecontact portion 4 moistened with water. As shown in the figure, it isapparent that in the spectral characteristics after having tea, theabsorbance and the change in spectral line shape are large, comparedwith the spectral characteristics at a normal time, and the higher theconcentration of tea, the larger the absorbance and the change inspectral line shape become. From this, it is conceived that because ofthe effects of the absorbance of tea, the measured results differentfrom those at a normal time are obtained when making the secondspectrometry after a subject has the tea, as shown in FIG. 3, and thecalculation of a glucose concentration is adversely affected.

Accordingly, in cases where the absorbance or the spectral line shape,which is obtained by calculating spectral characteristics after endingthe second spectrometry, is changed largely and the absorbance to thelight with a specific wave number is larger than a given value, it isvery likely that the first spectrometry has been made with a componentobstructive to the spectrometry contained between the lip mucosa and thecontact portion 4. Thus, the judging means 8 judges that the measuredresults in the first spectrometry are ineffective (S6).

In other words, the judging means 8 calculate the difference between thespectral characteristics and absorbance at a normal time and thoseobtained by the second spectrometry, which are shown in FIGS. 3 and 4.The spectral characteristics and absorbance at a normal time shown inFIGS. 3 and 4 are those calculated from the measured values obtainedthrough the following procedures: entering light emitted by the lightsource 1 into the concentration measuring contact 2 while keeping theconcentration measuring contact 2 clean; measuring the quantity of thelight, by the photodetector 6, that is passed through the concentrationmeasuring contact 2 to its outside and returned to the concentrationmeasuring contact 2 again. And these spectral characteristics andabsorbance are obtained in advance.

The judging means 8 judges whether the calculation of the concentrationof a specific component in a subject of measurement is effective or notby comparing the difference with the predetermined threshold.Specifically, if the difference is larger than the predeterminedthreshold, the judging means 8 judges the calculation of theconcentration of a specific component in a subject of measurement to beineffective, whereas if the difference is smaller than the predeterminedthreshold, it judges the calculation of the concentration of a specificcomponent in a subject of measurement to be effective.

The spectral characteristics and absorbance at a normal time of thisembodiment shown in FIGS. 3 and 4 are examples of reference values ofthis invention.

When the measuring means 8 judges the calculation of the concentrationof a specific component in a subject of measurement is ineffective,indicating means 11 gives a message that indicates the subject shouldgive his or her oral mucosa a good rinse. With this indication,measurement can be made again after the oral mucosa is rinsed with coldor warm water, which enables accurate measurement of a glucoseconcentration. After rinsing the oral mucosa, measurement is startedagain from the background measurement, S1.

When the measuring means 8 judges the calculation of the concentrationof a specific component in a subject of measurement is effective, thecalculating means 10 calculates, using the calibration curve 9, theconcentration of the glucose solution from the absorbance of the firstspectrometry (measurement 1) obtained by making the first spectrometry(measurement 1) and the background measurement (S7).

The measured value Im1 obtained by the first spectrometry may becorrected by calculating the effects of the obstructing component basedon the measured value Im2 obtained by the second spectrometry. FIG. 5shows a concentration measuring instrument that is capable of makingsuch corrections. In the figure, the same parts as those of FIG. 1 aredenoted by the same reference numerals and a detailed description ofthem will be omitted.

Input means 12 inputs the measured value obtained at the time ofbackground measurement and the measured values Im1, Im2 obtained by thefirst and second spectrometry from the photodetector 6. The input means12 calculates the absorbance to the light with a specific wave number inthe first spectrometry from the measured value Im1 obtained by the firstspectrometry and the measured value obtained by the backgroundmeasurement. Further, the input means 12 calculates the absorbance tothe light with a specific wave number in the second spectrometry fromthe measured value Im2 obtained by the second spectrometry and themeasured value obtained by the background measurement.

Then, correcting means 13 calculates a value by subtracting theabsorbance to the light with a specific wave number, which is calculatedfrom the measured value Im2 obtained in the second spectrometry, fromthe absorbance to the light with a specific wave number, which iscalculated from the measured value Im1 obtained in the firstspectrometry.

Calculating means 10 calculates the concentration of a glucose solution,that is, the concentration of a specific component from the valuecalculated by the correcting means 13 using a calibration curve 9. Doingthis enables the effects of obstructing components to be gotten rid of,and hence the accurate glucose concentration to be obtained.

The embodiment 1 has been described taking the case where the quantityof polarized light of a specific component is measured using a polarizer7, but the method of measuring such quantity of light is not limited tothis. Without the polarizer 7, the same effect as this embodiment can beobtained. However, since the component of p-polarized light oozes deeperinto a subject of measurement than that of s-polarized light, if theinstrument is provided with the polarizer 7 and the quantity of thep-polarized light component is measured using the polarizer 7, theconcentration of a specific component can be obtained with a higheraccuracy.

The calibration curve 9 may be a table in which the measured results areallowed to have one to one correspondence to the known concentrations ofglucose solutions or a mathematical equation by which the measuredresults are allowed to have one to one correspondence to the knownconcentrations of glucose solutions.

As described with FIG. 3, since light absorption of glucose reaches apeak in the wave number region of about 1200 cm⁻¹ to about 1000 cm⁻¹centered at about 1100 cm⁻¹, if the wave number region of about 1200cm⁻¹ to about 1000 cm⁻¹ centered at about 1100 cm⁻¹ is scanned in thebackground measurement, the first and second spectrometry, the glucoseconcentration can be measured with a higher accuracy.

Further, this embodiment has been described taking the case where a SiClight source is used as the light source 1, but the light source is notlimited to this. For example, tungsten is preferably used as the lightsource 1. A quantum cascade laser is more preferably used as the lightsource 1. These light sources are particularly suitable for measuringthe concentrations of substances, such as glucose, whose absorption wavenumbers are in the fingerprint region (mid-infrared region) of about1080 cm⁻¹ to about 1033 cm⁻¹, like the case where a SiC light source isused.

Further, this embodiment has been described taking the case wheregermanium is used as the material for the concentration measuringcontact 2, but the material for the concentration measuring contact 2 isnot limited to this. Silicon, which is capable of transmittingmid-infrared light, chemically stable and excellent in mechanicalstrength, can also be used as the material for the concentrationmeasuring contact 2.

When using silicon as the material for the concentration measuringcontact 2, a silicon single crystal substrate is used which istransparent to light with a wavelength of about 1.1 to about 10 microns.Silicon having small content of impurities, such as boron andphosphorus, and having resistivity of about 100 Ωcm or more isparticularly preferable. Silicon having resistivity of about 1500 Ωcm ormore is much more preferable. The silicon having such high resistivityhas high transmissivity at infrared wavelength of about 9 to about 10microns, and it is preferably used when measuring the concentration ofsubstances, such as glucose, whose absorption region is in thiswavelength band.

Preferably an antireflection film is provided on the surface of thelight input portion 3. As a material for the antireflection film,diamond-like carbon (DLC) or ZnSe is used. The thickness of theantireflection film is preferably about 1.1 to about 1.3 microns, morepreferably about 1.2 microns.

Preferably an antireflection film is provided on the surface of thelight output portion 5, like the light input portion 3.

Further, this embodiment has been described taking the case where an MCTphotodetector is used as the photodetector 6, but the photodetector isnot limited to this. A pyroelectric sensor may also be used as thephotodetector 6.

Further, this embodiment has been described taking the case where a wiregrid polarizer is used as the polarizer 7, but the polarizer is notlimited to this. An interference filter type of polarizer, whichtransmits the p-polarized light component and reflects the s-polarizedlight component, may also be used as the polarizer 7.

(Embodiment 2)

In the method of measuring the concentration of a specific component inaccordance with this embodiment, a step of judging whether or not thereexists a contaminant adhering on the surface of the concentrationmeasuring contact 2 is carried out before making background measurement.This step is to prevent the measured results from being adverselyaffected by the residues of the last measurement adhering on the surfaceof the contact portion 4, when making background measurement with thecontact portion 4 contaminated with them.

First, the polarizer 7 is used to allow the light of s-polarizedcomponent to pass and spectrometry of the s-polarized light component ismade with lip mucosa, as a subject of measurement, not brought intotight contact with the contact portion 4. Then the polarizer 7 isrotated at an angle of 90 degrees to allow the light of p-polarizedcomponent to pass and spectrometry of the p-polarized component is made.

Then, the judging means 8 carries out calculation according to theequation, Ip/Is, where Ip represents the measured value of the quantityof the p-polarized light component and Is the measured value of thequantity of the s-polarized light component. Calculating Ip/Is allowsthe evaluation of light absorption characteristics of the contaminantsadhering on the surface of the contact portion 4.

FIG. 6 shows the spectral characteristics obtained by carrying outcalculation according to the equation, Ip/Is. In the same figure, thegraph with “at a normal time” shows the spectral characteristicsobtained by making spectrometry while keeping the surface of the contactportion 4 clean and moistening the same with water. The graph with“after having atea” shows the spectral characteristics obtained bymaking spectrometry with the contact portion, which has been broughtinto tight contact with a person's lip mucosa after the person has tea,kept out of contact with the lip mucosa. It is apparent from the figurethat there is a significant difference between the spectralcharacteristics at a normal time and after having tea.

Accordingly, when the value of Ip/Is is the same as or larger than agiven value, the judging means 8 judges that there exists a contaminantadhering on the surface of the contact portion 4. Specifically, when thevalue of Ip/Is is in the range of about 0.9 to about 1.1, the judgingmeans 8 judges that there exists no contaminant adhering on the surfaceof the contact portion 4. And when the value of Ip/Is is outside theabove range, the judging means 8 judges that there exists a contaminantadhering on the surface of the contact portion 4. Thus, the judgingmeans 8 judges whether or not the calculation of the concentration of aspecific component in a subject of measurement is effective.

When the judging means 8 judges that there exists a contaminant adheringon the surface of the contact portion 4, the indicating means 11 gives amessage that indicates the surface of the contact portion 4 should becleaned. If the measurement is made again after the surface of thecontact portion 4 is cleaned, the accuracy of the glucose concentrationmeasurement can be improved.

When the judging means 8 judges that there exists no contaminantadhering on the surface of the contact portion 4, the same operation asthat of the embodiment 1 is carried out.

In this measurement, it is preferable to set the incident angle θ of thelight entered into the contact portion 4 so that the value, z/λ,calculated using the following equation (1) becomes about 0.25 or more.

$\begin{matrix}{\frac{Z}{\lambda} = \frac{1}{2\;\pi\sqrt{{n\; f^{2}\mspace{11mu}\sin^{2}\;\theta} - {n\; c^{2}}}}} & \left( {{Mathematical}\mspace{14mu}{Equation}\mspace{14mu} 1} \right)\end{matrix}$wherein z represents the depth (unit: micron) to which the light enteredinto the contact portion oozes into the contaminant adhering on thesurface of the contact portion, λ the wavelength (unit: micron) of thelight entered into the contact portion, nf the refractive index of thecontact portion, θ the incident angle of the light entered into thecontact portion, and nc the refractive index of the contaminant.

For example, in cases where the contaminant adhering on the surface ofthe contact portion is a tea, the wavelength of the light is about 9.6microns and the refractive index of the tea nc is about 1.24, ifgermanium, whose refractive index nf is about 4, is used for the contactportion, the incident light θ which satisfies z/λ=0.25 is about 45degrees. If light is entered into the contact portion at such anincident angle, the absorbance of the contaminant differs largelydepending on whether the incident light is the s-polarized light or thep-polarized light. The presence or absence of the contaminant can bedetected by the difference in absorbance created depending on whetherthe incident light is the s-polarized light or the p-polarized light.Specifically, the s-polarized light oozes into the contaminant only to ashallower portion, whereas the p-polarized light oozes into thecontaminant to a deeper portion. And the s-polarized light is hardlyaffected by the concentration of a specific component contained in thecontaminant adhering on the surface of the contact portion. In otherwords, the measurement of the quantity of the s-polarized lightcorresponds to the measurement of background in the prior art and themeasurement of the quantity of the p-polarized light corresponds to themeasurement of spectral characteristics of the contaminant in the priorart. Thus, the presence or absence of the contaminant can be detected bymeasuring the quantities of the s-polarized light and p-polarized light.

This method is effective when the incident angle of the light enteredinto the contact portion is 45 degrees or less, but preferably theincident angle is larger than critical angle. If the incident angle issmaller than critical angle, the light does not satisfy the totalreflection requirements; as a result, the light is scattered in thecontaminant adhering on the surface of the contact portion, whichdecreases the quantity of light returned to the contact portion, and inaddition, the optical path difference between the p-polarized light andthe s-polarized light is decreased. Experiments showed that when z/λ=0.9or more, in other words, when using germanium for the contact portionand setting the incident angle to about 21 degrees or about 20 degrees,particularly satisfactory results were obtained, and when setting theincident angle to about 19 degrees, much more satisfactory results wereobtained.

Although this embodiment has been described taking the case where thevalue, Ip/Is, is used to carry out the step of judging the presence orabsence of a contaminant adhering on the surface of the concentrationmeasuring contact, the value is not limited to this. When using a valuecalculated according to the equation, log₁₀ (Ip/Is), the same effect canbe obtained. Further, the judgment may be made using a value calculatedaccording to the equation, Is/Ip or log₁₀ (Is/Ip), and when the value isthe same as or smaller than a given value, a contaminant is judged to bepresent on the surface of the concentration measuring contact. In caseswhere the value, Is/Ip, is used to judge whether or not there exists acontaminant on the surface of the concentration measuring contact, ifthe value of Is/Ip is in the range of about 0.9 to about 1.1, thejudging means 8 judges that there exists no contaminant adhering on thesurface of the concentration measuring contact. And when the value ofIs/Ip is outside the above range, the judging means 8 judges that thereexists a contaminant adhering on the surface of the concentrationmeasuring contact.

Further, though the embodiment 2 has been described taking the casewhere the same operation as that of the first embodiment is carried outwhen the judging means 8 judges that there exists no contaminantadhering on the surface of the contact portion, the operation is notlimited to this. When the judging means 8 judges that there exists nocontaminant adhering on the surface of the contact portion, the steps 4and 5 of the embodiment 1 may be omitted.

Further, though the embodiment 2 has been described taking the casewhere the concentration of glucose, as a specific component in a subjectof measurement, is measured, the subject of measurement is not limitedto this. The method is effective when measuring the concentration ofglucose not only in a glucose solution, but also in blood plasma, aliving body, etc. When the specific component in a subject ofmeasurement is a component other than glucose, such as cholesterol,ethanol or the derivative of cholesterol, this embodiment can beeffectively applied. However, the specific component in a subject ofmeasurement is changed, the wavelength of light to be measured is alsochanged.

Specifically, when the specific component of a subject of measurement ischolesterol or the derivative of cholesterol, since the absorptionwavelength of cholesterol is 1500 nm or 1700 nm, a light source thatemits light with such a wavelength should be used as a light source 1 ora photodetector that detects light with such a wavelength should beused. When the specific component of a subject of measurement isethanol, since the absorption wave number of ethanol is about 1240 cm⁻¹or about 1400 cm⁻¹, a light source that emits light with such a wavenumber should be used as a light source or a photodetector that detectslight with such a wave number should be used. When the specificcomponent of a subject of measurement is different from the abovedescribed ones, if a light source that emits light with an absorptionwave numbers of the specific component of the subject of measurement isused or a photodetector that detects light with such a wave number isused, the concentration of the specific component in the subject ofmeasurement can be measured, like the above described components.

INDUSTRIAL APPLICABILITY

According to this invention, a concentration measuring instrument and amethod of measuring the concentration of a specific component in asubject of measurement can be provided which enables a highly accuratemeasurement of the concentration of specific components in subjects ofmeasurement even when the concentration measuring contact of aconcentration measuring instrument is contaminated with drinks or thelike, because the method includes a judging step of judging whether ornot there exists a substance, which is obstructive to the measurement ofthe concentration of specific components, adhering on the surface of thecontact portion of the concentration measuring contact.

1. A concentration measuring instrument, comprising: a main body thathas a concentration measuring contact, a light source that emits lightand enters the light into the concentration measuring contact, and aphotodetector; and judging means that calculates the difference between(1) a non-contact measured value, a value, measured by the photodetectorwhile keeping a subject of measurement out of contact with theconcentration measuring contact, of the quantity of light which isemitted and entered by the light source into the concentration measuringcontact, passed through or oozed from the concentration measuringcontact to the outside thereof and returned to the concentrationmeasuring contact and (2) a reference value, a value, measured by thephotodetector while keeping the concentration measuring contact clean,of the quantity of the light which is emitted and entered by the lightsource into the concentration measuring contact, passed through or oozedfrom the concentration measuring contact to the outside thereof andreturned to the concentration measuring contact, and judges whether acalculation of the concentration of a specific component in the subjectof measurement is effective or not by comparing the calculateddifference with a threshold.
 2. The concentration measuring instrumentaccording to claim 1, further comprising calculating means, wherein thephotodetector measures, while keeping the subject of measurement incontact with the concentration measuring contact, the quantity of lightwhich is emitted and entered by the light source into the concentrationmeasuring contact, passed through the concentration measuring contactinto a subject of measurement, transmitted in the subject ofmeasurement, and returned to the concentration measurement contact, whenthe judging means judges the calculation of the concentration of aspecific component in the subject of measurement to be effective, andthe calculating means calculates the concentration of a specificcomponent in the subject of measurement based on a contact measuredvalue, a value obtained by making measurements while keeping the subjectof measurement in contact with the concentration measuring contact. 3.The concentration measuring instrument according to claim 1, furthercomprising indicating means, wherein the indicating means gives amessage that indicates the surface of the concentration measuringcontact should be cleaned, when the judging means judges the calculationof the concentration of a specific component in the subject ofmeasurement to be ineffective.
 4. A concentration measuring instrument,including: a main body that has a concentration measuring contact, alight source that emits light and enters the light into theconcentration measuring contact, and a photodetector; and judging meansthat calculates the difference between (1) a non-contact measured value,a value, measured by the photodetector, of the quantity of light whichis emitted and entered by the light source into the concentrationmeasuring contact once brought into contact with a subject ofmeasurement and then kept out of contact the same, passed through oroozed from the concentration measuring contact to the outside thereofand returned to the concentration measuring contact and (2) a referencevalue, a value, measured by the photodetector while keeping theconcentration measuring contact clean, of the quantity of light which isemitted and entered by the light source into the concentration measuringcontact, passed through or oozed from the concentration measuringcontact to the outside thereof and returned to the concentrationmeasuring contact, and compares the calculated difference with athreshold so as to judge whether a calculation of the concentration of aspecific component in the subject of measurement is effective or not. 5.The concentration measuring instrument according to claim 4, furtherincluding calculating means, wherein the photodetector measures, whilekeeping the subject of measurement in contact with the concentrationmeasuring contact, the quantity of light which is emitted and entered bythe light source into the concentration measuring contact, passedthrough the concentration measuring contact into the subject ofmeasurement, transmitted in the subject of measurement, and returned tothe concentration measurement contact and when the judging means judgesthe calculation of the concentration of a specific component in thesubject of measurement to be effective, the calculating means calculatesthe concentration of the specific component in the subject ofmeasurement based on a contact measured value, which is a value measuredwhile keeping the subject of measurement in contact with theconcentration measuring contact.
 6. The concentration measuringinstrument according to claim 4, further including indicating means,wherein the indicating means gives a message that indicates the subjectof measurement should be cleaned, when the judging means judges thecalculation of the concentration of a specific component in the subjectof measurement to be ineffective.
 7. A concentration measuringinstrument, incuding: a main body that has a concentration measuringcontact, a light source that emits light and enters the light into theconcentration measuring contact and a photodetector; inputting meansthat inputs (1) a contact-measured value, a value, measured by thephotodetector, of the quantity of light which is emitted and entered bythe light source into the concentration measuring contact in contactwith a subject of measurement, passed through the concentrationmeasuring contact into the subject of measurement, transmitted in thesubject of measurement, and returned to the concentration measuringcontact and (2) a non-contact measured value, a value, measured aftermeasuring the contact-measured value by the photodetector and keepingthe subject of measurement out of contact with the concentrationmeasuring contact, of the quantity of light which is emitted and enteredby the light source into the concentration measuring contact, passedthrough or oozed from the concentration measuring contact to the outsidethereof and returned to the concentration measuring contact; correctingmeans that corrects the contact-measured value using thenon-contact-measured value; and calculating means that calculates theconcentration of a specific component contained in the subject ofmeasurement based on the corrected result.
 8. The concentrationmeasuring instrument according to claim 7, wherein the correcting meanscalculates a value by subtracting the absorbance of the light with aspecific wave number, which is calculated from the non-contact measuredvalue, from the absorbance of the light with a specific wave number,which is calculated from the contact-measured value, and the calculatingmeans calculates the concentration of the specific component containedin the subject of measurement based on the value calculated by thecorrecting means.
 9. The concentration measuring instrument according toany one of claims 1 to 7, wherein the concentration measuring contact isan attenuated total reflectance device and the light entered into theconcentration measuring contact is evanescent light oozed from theattenuated total reflectance device.
 10. The concentration measuringinstrument according to any one of claims 1 to 7, wherein the subject ofmeasurement is a living body tissue and the specific component isglucose, ethanol, cholesterol, or the derivative of cholesterol.
 11. Theconcentration measuring instrument according to any one of claims 1 to7, wherein the photodetector scans the light in the wave number regionof about 1000 cm⁻¹ to about 1200 cm⁻¹ centered at about 1100 cm⁻¹. 12.The concentration measuring instrument according to any one of claims 1to 6, wherein the judging means judges the calculation of theconcentration of a specific component in the subject of measurement tobe ineffective, when the absorbance to the light with a specific wavenumber which is obtained from the non-contact-measured value is largerthan a predetermined value.
 13. The concentration measuring instrumentaccording to any one of claims 1 to 6, wherein the measurement of thenon-contact-measured value is to measure, by the photodetector, thequantities of the p-polarized light component and the s-polarized lightcomponent of the light which is emitted and entered by the light sourceinto the concentration measuring contact out of contact with the subjectof measurement, passed through or oozed from the concentration measuringcontact to the outside thereof, and returned to the concentrationmeasuring contact, the judging means judges whether or not there existsa contaminant adhering on the surface of the concentration measuringcontact, based on the measured values of the quantities of thep-polarized light component and the s-polarized light component, and thejudgment of whether the calculation of the concentration of a specificcomponent in the subject of measurement is effective or not is to judgewhether or not there exists a contaminant adhering on the surface of theconcentration measuring contact.
 14. The concentration measuringinstrument according to claim 13, wherein the judging means carries outcalculation according to the equation, Ip/Is or log₁₀ (Ip/Is), where Iprepresents the measured value of the quantity of the p-polarized lightcomponent and Is the measured value of the quantity of the s-polarizedlight component, and judges that there exists a contaminant adhering onthe surface of the concentration measuring contact, when the calculatedvalue is the same as or more than a given value.
 15. The concentrationmeasuring instrument according to claim 14, wherein the judging meansjudges that there exists no contaminant adhering on the surface of theconcentration measuring contact when the value of Ip/Is is in the rangeof about 0.9 to about 1.1.
 16. The concentration measuring instrumentaccording to claim 13, wherein the judging means carries out calculationaccording to the equation, Is/Ip or log₁₀ (Is/Ip), where Ip representsthe measured value of the quantity of the p-polarized light componentand Is the measured value of the quantity of the s-polarized lightcomponent, and judges that there exists a contaminant adhering on thesurface of the concentration measuring contact, when the calculatedvalue is the same as or less than a given value.
 17. The concentrationmeasuring instrument according to claim 16, wherein the judging meansjudges that there exists no contaminant adhering on the surface of theconcentration measuring contact when the value of Is/Ip is in the rangeof about 0.9 to about 1.1.
 18. A method of measuring the concentrationof a specific component in a subject of measurement utilizing aconcentration measuring instrument that has a concentration measuringcontact, a light source that emits light and enters the light into theconcentration measuring contact and a photodetector, comprising: anon-contact measuring step of measuring, by the photodetector whilekeeping the subject of measurement out of contact with the concentrationmeasuring contact, the quantity of light which is emitted and entered bythe light source into the concentration measuring contact, passedthrough or oozed from the concentration measuring contact to the outsidethereof and returned to the concentration measuring contact; and ajudging step of judging whether a calculation of the concentration ofthe specific component in the subject of measurement is effective or notby comparing with a threshold a calculated difference obtained bysubtracting (2) a reference value, a value, measured by thephotodetector while keeping the concentration measuring contact clean,of the quantity of light which is emitted and entered by the lightsource into the concentration measuring contact, passed through or oozedfrom the concentration measuring contact to the outside thereof andreturned to the concentration measuring contact from (1) a non-contactmeasured value, a value measured in the non-contact measuring step. 19.A method of measuring the concentration of a specific component in asubject of measurement utilizing a concentration measuring instrumentthat has a concentration measuring contact, a light source that emitslight and enters the light into the concentration measuring contact anda photodetector, comprising: a non-contact measuring step of measuringby the photodetector the quantity of light which is emitted and enteredby the light source into the concentration measuring contact which isonce brought into contact with the subject of measurement and then keptout of contact the same, passed though or oozed from the concentrationmeasuring contact to the outside thereof and returned to theconcentration measuring contact; and a judging step of judging whether acalculation of the concentration of a specific component in the subjectof measurement is effective or not by comparing with a threshold acalculated difference obtained by subtracting (2) a reference value, avalue, measured by the photodetector while keeping the concentrationmeasuring contact clean, of the quantity of light which is emitted andentered by the light source into the concentration measuring contact,passed though or oozed from the concentration measuring contact to theoutside thereof and returned to the concentration measuring contact from(1) a non-contact measured value, a value measured in the non-contactmeasuring step.
 20. A method of measuring the concentration of aspecific component in a subject of measurement, comprising: a contactmeasuring step of measuring by photodetector the quantity of light whichis emitted and entered by a light source into a concentration measuringcontact in contact with the subject of measurement, passed through theconcentration measuring contact into the subject of measurement,transmitted in the subject of measurement, and returned to theconcentration measuring contact; a non-contact measuring step ofmeasuring by the photodetector the quantity of light which is emittedand entered by the light source into the concentration measuringcontact, which is kept out of contact with the subject of measurementafter the contact measuring step, passed through or oozed from theconcentration measuring contact to the outside thereof, and returned tothe concentration measuring contact; and a calculating step ofcalculating, after correcting the measured result obtained in thecontact measuring step with the measured result obtained in thenon-contact measuring step, the concentration of the specific componentin the subject of measurement based on the corrected result.